Corrosion inhibiting compositions and processes



United States Patent 3,204,695 CORROSION INHTBTTING CQMPOSITIONS ANDPROCESSES Charles E. Tippett, Chicago, Ill., assignor to Armour andCompany, Chicago, 11L, a corporation of Delaware No Drawing. Filed June27, 1962, Ser. No. 205,559 13 Claims. (Cl. 252-149) This inventionrelates to corrosion inhibiting compositions and processes, and moreparticularly to compositions and methods for inhibiting corrosion andpitting caused by aqueous solutions of pickling and cleaning acids, suchas sulfuric, sulfamic, phosphoric, citric, etc. acids.

In formulating a corrosion inhibiting compound for use in aqueoussolutions of metal corroding acids, major problems have existed withrespect to the safety hazard, necessity for solvents, unpleasant odorsdeveloped, as well as effectiveness in reducing corrosion. I havediscovered that by employing quaternaries of alkoxylated amines incombination with dibutylthiourea, a formulation is provided havingsufficient solubility at use concentrations as to eliminate therequirements of a solvent, while at the same time the product has a highflash point which meets all safety hazard requirements, and thecomposition further gives extremely high protection against corrosion.

A primary object, therefore, is to provide a composition and processmeeting safety hazard requirements and providing effective protectionagainst corrosion by aqueous acid solutions. A further object is toprovide a composition which eliminates the need for solvents while atthe same time having a high flash point providing for the utmost ofsafety in use. A further object is to provide a composition in which theactive materials are effectively dispersed for yielding high efiiciencyin use. Yet another object is to provide a composition in which thequaternary ammonium compound may be one hundred percent active. Otherspecific objects and advantages will appear as the specificationproceeds.

In one embodiment of the invention, dibutylthiourea is mixed with acompound having the following structure:

wherein R is an aliphatic hydrocarbon radical having between 6 and 22carbon atoms, R is an alkylene radical having between 2 and 3 carbonatoms, R" is an alkyl radical having between 1 and 3 carbon atoms, X isa halogen, and x and y are integers having a sum total varying between 2and 50.

It is preferred to employ in combination with the dibutylthiourea, anethoxylated quaternary ammonium compound or a propoxylated quaternaryammonium compound, and the range of moles for the ethylene oxide orpropylene oxide is 2 to 50 moles. I prefer to employ 2 to 25 moles ofthe ethylene oxide or propylene oxide. Best results have been obtainedwhen there are about 2 to 15 moles of the ethylene oxide or propyleneoxide.

The ethoxylated quaternary ammonium compound or propoxylated quaternaryammonium compound may be used with the dibutylthiourea in varyingproportions, the preferred range being -50% by weight of thedibutylthiourea to 90-50% by weight of the ethoxylated quaternaryammonium compound. Best results have been obtained where thedibutylthiourea is 25% and the ethoxylated ammonium compound is 75% byweight.

New results achieved by the new formulation or composition are thatsolubility is provided without the use for a solvent and the flash pointof the composition or mix- 3,204,095 Patented Dec. 27, 1966 ture is inexcess of 340 F. Further, the formulation may contain a activequaternary ammonium compound.

The composition consisting of the ethoxylated quaternary ammoniumcompound and the dibutylthiourea may be used without further additives.However, the com position may be usefully employed with a dispersantmaterial, such as a cationic or non-ionic surface active agent,including a polyethoxylated fatty acid, polyeth oxylated diamines, etc.Usually good results have been obtained by the use of polyethoxylatedrosin-fatty acids.

As a specific example, the following may be set out:

Percent Ethoquad C/25 (ethoxylated quaternary ammonium compound of cocoorigin having 15 moles of ethylene oxide) 71.2 Dibutylthiourea 23.8Ethofat 242/25 (polyethoxylated 70% rosin-fatty acids having 15 moles ofethylene oxide) 5.0

In the above formulation, Propoquad C/ 25 (quaternary ammonium compoundfrom coco origin having 15 moles of propylene oxide) is substituted withequal results for Ethoquad C/25.

The compositions described may be employed with any of the pickling orcleaning acids, including sulfuric, phosphoric, sulfamic, citric, etc.acids.

In preparing the composition, I prefer to acidulate the ethoxylated orpropoxylated quaternary ammonium compound with hydrochloric or sulfuricacid to a pH of about 4.5-5.5 before the dibutylthiourea is added. Bythis procedure, it is found that superior corrosion protection isobtained.

Specific examples illustrative of the processes and com positions may beset out as follows:

Example I Mild steel coupons were exposed to an acid at a previouslydetermined concentration and at a given temperature for 6 hours. At theend of the test period, the coupon was removed from the acid, cleaned,and reweighed. The corrosion rate is calculated on a weight loss basisand expressed in lb./ft. /day.

The mild steel coupons were wiped free of excess grease with a cleancloth, degreased in isooctane, and agitated in a ball mill in thepresence of mesh Alundum powder for 3 days. Just before using, thecoupons were removed from the ball mill, washed in hot alcohol, anddried in hot acetone.

A number of compositions were prepared and tested in a 15% sulfuric acidsolution; 0.25% inhibitor concentration (basis acid concentration), andat a temperature of 200 F., using the mild steel coupons describedabove. The compositions were as follows:

Percent (1) Ethoquad C/25 71.2 Dibutylthiourea 23.8 Ethofat 242/25 5.0

(2) The composition was as in (1) except that Ethoquad C/ 12(ethoxylated quaternary ammonium compound of coco origin having 2 molesof ethylene oxide) was substituted for Ethoquad C/ 25 (3) Thecomposition was as in (1) except that Propoquad C/ 12 (propoxylatedquaternary ammonium compound of coco origin having 2 moles of propyleneoxide) was substituted for Ethoquad C/ 25.

(4) The composition was as in 1) except that for the Ethoquad C/ 25,Propoquad C/25 (propoxylated quaternary ammonium compound of coco originhaving 15 moles of propylene oxide) was substituted.

(5) The composition was as in (1) except that for 3 the Ethoquad C/25,Propo'quad HT/12 (propoxylated quaternary ammonium compound ofhydrogenated tallow origin having 2 moles of propylene oxide) wassubstituted.

(6) The composition was as in except that Propoquad HT/25 (propoxylatedquaternary ammonium compound having 15 moles of propylene oxide) wasused in place of Propoquad HT/ 12.

The results were as follows:

Lb./ft. /day Control 2.52 Propoquad HT/ 12 .0272 Propoquad HT/25 .0462Propoquad C/l2 .0219 Propoquad C/25 .0242 Ethoquad C/12 .0196 EthoquadC/25 .0114

Example II Armohib 31 was made up of the following chemicals:

Percent Ethoquad C/25 71.2 Dibutylthiourea 23.8 Ethofat 242/25 5.0

In preparing the composition, the Ethoquad C/25 was acidulated to a pHof 4.55.5, as indicated by a pH meter, the acidulation being withconcentrated sulfuric acid. The correct amounts of Ethofat 242/25 anddibutylthiourea were then added to the Ethoquad C/25 and the mixtureheated to approximately 150 F. until the dibutylthiourea was melted. Themixture was stirred during the heating period. A test made after a48-hour period showed that no unpleasant or offensive odor wasdeveloped.

In testing the above composition, 160 ml. of 15% sulfuric acid wereplaced in an 8 oz. French square bottle and a 0.06% concentration (onthe basis of total solution) of Armohib 31 added. The test cell wasplaced in a constant temperature oil bath and heated to 200 F. When thetest cell reached the desired temperature, a metal coupon which hadpreviously been cleaned and weighed was placed in the acid mixture. Atthe end of a 6-hour test period, the coupon was removed, cleaned, andreweighed. The corrosion rate was calculated on a weight loss basis andexpressed in lb./ft. /day. In a series of tests, it was found that thecorrosion rate was always less than .027.

The above composition (Armohib 31) was found to have the followingphysical properties.

Activity 100%. Cloud point 28 F. Pour point 24 F. Flash point Over 340F. Specific gravity 25 C. 1.042. Solubility:

Water Dispersible to 1%. Acid Dispersible (soluble at useconcentration). Physical appearance Viscous amber colored liqquid.Lb./gal. 8.72.

Example III The test was carried on as described in Example 11 exceptthat phosphoric acid at temperatures of 165 F. and 200 F. and at acidpercents varying from 20-10% was employed, the results in terms oflb./ft. /day being substantially less than .027

Example IV Tests were made as described in Example II with citric acidat temperatures of 165 F. and at 200 F., with the citric acid being usedat l0-20%, and with the results in the terms of lb./ft. /day being againsubstantially less than .027.

Example V A further test was made using a mixture of phosphoric acid andsulfuric acid at room temperatures and with results comparable to thosedescribed in Example II.

Example VI Tests employing a composition consisting of 25%dibutylthiourea and 75% Ethoquad C/25 were carried out as described inExample 11, no dispersant chemical being employed, and the corrosionrate was found to be substantially less than .027 lb./ft. /day.

Example VII Tests as described in Example VI, substituting Propoquad C/25 and C/ 12 and Propoquad HT/ 12 and HT/ 25, likewise give a corrosionrate of .0272 lb./ft. /day.

Example VIII Tests made with varying amounts of dibutylthiourea inranges between 10% and 50% by weight and of the Ethoquad and Propoquadcompounds in ranges between and 50% by weight demonstrated that theranges were not critical in that improvement was obtained throughoutthese ranges, but the solubility was best, and best results wereobtained in the proportions of about A to /3 of the dibutylthiourea toabout a to /3 of the ethoxylated quaternary ammonium compound. Asalready stated, the best results were obtained when the proportions were25 of the dibutylthiourea and 75% of the propoxylated quaternaryammonium compound.

While in the foregoing specification I have set forth compositioningredients and procedure in considerable detail for the purpose ofillustrating embodiments of my invention, it will be understood thatsuch details of composition and procedure may be varied widely by thoseskilled in the art without departing from the spirit of my invention.

I claim:

1. A composition for inhibiting corrosion of ferrous metals in contactwith aqueous solutions of corroding acids, consisting essentially ofdibutylthiourea and from about 50 to 90 weight percent, based upon totalweight of the composition, of a compound having the structure:

wherein R is an aliphatic hydrocarbon radical having between 6 and 22carbon atoms, R is an alkylene radical having between 2 and 3 carbonatoms, R is an alkyl radical having between 1 and 3 carbon atoms, X is ahalogen, and x and y are integers having a sum total varying between 2and 50.

2. A composition for inhibiting corrosion of ferrous metals in contactwith aqueous solutions of corroding acids, consisting essentially ofdibutylthiourea and an ethoxylated quaternary ammonium compound havingan aliphatic hydrocarbon radical with between 6 and 22 carbon atoms inthe ratio of 10-50% by weight of dibutylthiourea and 90-50% by weight ofthe ethoxylated quaternary ammonium compound.

3. The composition of claim 2 in which the proportion by weight of thedibutylthiourea is A to /s of the composition and the proportion byweight of the ethoxylated compound is about to of the composition.

4. The composition of claim 2 in which the proportion by weight of thedibutylthiourea is about 25 and that of the ethoxylated quaternaryammonium compound is about 75 of the composition.

5. The composition of claim 2 in which the ethoxylated quaternaryammonium compound is an ethoxylated quaternary ammonium compound having2 to 50 moles of ethylene oxide.

6. The composition of claim 5 in which the ethoxylated compound has 2 to15 moles of ethylene oxide.

7. A composition for inhibiting corrosion of ferrous metals in contactwith aqueous solutions of corroding acids, consisting essentially ofdibutylthiourea and a propoxylated quaternary ammonium compound havingan aliphatic hydrocarbon radical of from 6 to 22 carbon atoms in theratio of 50% by weight of dibutylthiourea and 9050% by Weight of thepropoxylated quaternary ammonium compound, said quaternary ammoniumcompound being propoxylated with from 2 to 50 moles of propylene oxide.

8. The composition of claim 7 in which the propoxylated quaternaryammonium compound has about 2 to moles of propylene oxide.

9. In a process for inhibiting corrosion of ferrous metals in contactwith aqueous solutions of corroding acids, the steps of adding to suchsolutions a corrosion inhibiting composition consisting essentially ofdibutylthiourea and an ethoxylated quaternary ammonium compound havingan aliphatic hydrocarbon radical with between 6 and 22 carbon atoms inthe proportions of 105 0% by weight of dibutylthiourea and 90-50% of theethoxylated quaternary ammonium compound.

10. The process of claim 9 in Which the dibutylthiourea is added in theproportion of about 25% and the ethoxylated quaternary ammonium compoundin the proportion of about 75%.

11. In the preparation of a corrosion inhibiting composition, the stepsof acidulating an ethoxylated quaternary ammonium compound having analiphatic hydrocarbon radical with between 6 and 22 carbon atoms to a pHof 4.55.5, and then mixing therewith dibutylthiourea in the proportionsof about 10-50% of the dibutylthiourea to 9050% by weight of theethoxylated quaternary ammonium compound.

12. In a process for inhibiting corrosion of ferrous metals in contactwith aqueous solutions of corroding acids, the steps of adding to suchsolutions a corrosion inhibiting composition consisting essentially ofdibutylthiourea and a propoxylated quaternary ammonium com pound havingan aliphatic hydrocarbon radical with between 6 and 22 carbon atoms inthe proportions of 10-- by Weight of dibutylthiourea and 50-90% of thepropoxylated quaternary ammonium compound.

13. In the preparation of a corrosion inhibiting composition, the stepsof acidulating a propoxylated quaternary ammonium compound having analiphatic hydrocarbon radical with between 6 and 22 carbon atoms to a pHof 4.5-5.5, and then mixing therewith dibutylthiourea in the proportionsof about 1050% of the dibutylthiourea to 50-90% by weight of thepropoxylated quaternary ammonium compound.

References Cited by the Examiner UNITED STATES PATENTS 2,214,352 9/1940Schoeller et al. 260567.6 2,759,975 8/1956 Chiddix et al. 252l523,047,510 7/1962 Cizek 252-149 3,056,746 10/1962 Brightly 252--1463,088,796 5/1963 Kahler et al. 252357 SAMUEL H. BLECH, Primary Examiner.

JULIUS GREENWALD, ALBERT T. MEYERS,

Examiners. W- E. SCHULZ, Assistant Examiner.

1. A COMPOSITION FOR INHIBITING CORROSION OF FERROUS METALS IN CONTACTWITH AQUEOUS SOLUTIONS OF CORRODING ACIDS, CONSISTING ESSENTIALLY OFDIBUTYLTHIOUREA AND FROM ABOUT 50 TO 90 WEIGHT PERCENT, BASED UPON TOTALWEIGHT OF THE COMPOSITION, OF A COMPOUND HAVING THE STRUCTURE: